Balers are machines that pick-up crop that has been deposited in windrows or swathes and compact it into bales. The crop may be, for example, straw that has been deposited by a combine harvester or grass cut by a mowing machine. The balers themselves can be self-propelled or towed by a tractor and the bales can be round or square. The present invention is particularly concerned with square balers but is not restricted to any particular crop.
As with all balers, a square baler has a pick-up mechanism for raising the crop from the ground, a crop transport mechanism and a baling chamber. The transport mechanism in a square baler comprises an intake duct that acts as a pre-baling chamber into which the crop is introduced by the pick-up and in which the crop is pre-compressed by a packer. Alternatively a cutter could be provided at the lower end of the intake duct to chop the crop before it is formed into bales.
When a desired degree of compression has been reached in the intake duct, as detected usually by movement of a spring biased flap in the wall of the intake duct, a so-called stuffer is actuated to upload the contents of the intake duct into a square baling chamber where it is compressed further to form a bale. The bale is built up in slices in this way until the desired bale length is reached.
The compression of the crop in the baling chamber is carried out by a constantly reciprocating plunger which pushes the bale being formed against a resistance offered by a previously formed bale that is in the process of being ejected from the baling chamber. To set its resistance to movement, the previously formed bale is gripped from the sides and/or from above by walls to which a hydraulic pressure is applied in a direction to compress the bale.
The hydraulic pressure that is varied to regulate the density of the bale being formed can be set manually or automatically. In the latter case, instead of manually setting the magnitude of the hydraulic pressure, the operator sets a desired degree of resistance. The actual degree of resistance is measured, for example from the reaction force on the plunger, and compared with the desired resistance to derive an error signal. The hydraulic pressure is then varied in a closed feedback control loop to minimise the error signal and thereby attain the desired resistance set point.
Once a bale in the baling chamber reaches the desires size, lengths of twine are wrapped around the bale and they are knotted to complete the baling process.
Because square balers are well known and well documented in the prior art, it is not believed necessary to describe it in greater detail within the present context.
There are numerous operating parameters that can be set by the operator that affect the baling operation, this term being used herein to refer both the properties of the bales themselves and to the efficiency of the baling operation, for example the weight of crop baled in a given time.
A bale's properties are unacceptable for example if the bale density is too low or too high, or if the bale length or weight is outside a specified range, or if the bale density is not uniform across the width of the bale.
The operating parameters that the operator can set and that affect the baling quality are for example the tractor speed, the steering angle and also machine settings such as the degree of compression in the pre-baling chamber etc. Because of the large number of operating parameters to be set and the fact that the settings are not all independent of one another, it is difficult for an operator, especially one who is inexperienced, to set the values of all the parameters correctly at the same time as driving at the correct speed and in the correct direction.